The activity, efficiency, stability, and durability of a catalyst in a reaction, for example, the manufacture of alkylene oxides, depend upon the chemical, physical, and structural properties of the catalyst precursors, i.e., the support material and the support particles, and the nature and distribution of the catalytic material on the support. Desirably, the properties of the support material that enhance catalytic activity are retained by the support particles. In general, the support and catalyst comprising small amounts of the catalytic material on the support have essentially the same physical and structural properties with slight differences.
A need exists for a catalyst support having not only the porosity characteristics necessary for proper catalyst loading but good structural properties as well such as crush strength and attrition resistance. In addition, the material comprising the support preferably should be extrudable, in the green state, into complex shapes when desired to provide, for example, higher surface contact area or lower pressure drop across the reactor bed.
A catalyst support needs to possess, in combination, at least a minimum surface area on which the silver component may be deposited, sufficient water absorption and reasonable crush strength. However, a difficulty in optimizing these characteristic lies in the fact that an improvement in one property can result in a reduction in another. Thus optimization of crush strength, for example, may lead to low porosity.
Typically, support materials made from alkaline earth metal carbonate have relatively poor mechanical properties, particularly poor crush strength. Therefore, there is a need for an alkaline earth metal carbonate support with the porosity characteristics necessary for proper catalyst loading, while having improved mechanical properties, especially crush strength.